For the most part in the Hard-Boiled Wonderland portion of the narrative, the INKlings are unseen creatures dwelling in the subway tunnels, sewers, and other underground sections beneath Tokyo. There are accounts of sewer and subway workers that mysteriously disappear, as though carried away by something malignant. The Calcutec first hears of them when making his way to the Professor's underground base which is deep within INKling territory although the creatures themselves are repelled by sound-waves produced by the Professor's machinery.

They persist as a threatening force, taking advantage of the darkness and humanity's weak-to-nonexistent night vision to do as they may-although they will never go above to the surface and flee any lights shone in their direction. On a much more menacing level, it is revealed that the INKlings have a base under each major governmental building in Japan, thereby using them as leverage. Should anyone in Japan attempt to exterminate or remove the INKlings, they will drag every governmental official into the darkness below.